Novel high temperature proton conducting fuel cells: Production of La0.995Sr0.005NbO4-δ electrolyte thin films and compatible cathode architectures

For breakthrough development in solid oxide fuel cells, novel cell architectures integrating better performing materials and cost-effective manufacturing processes with potential for mass production must be realised. The present work addresses this on the basis of the recent discovery of acceptor doped rare-earth ortho-niobate proton conductors and the development of a versatile fabrication process. La0.995Sr0.005NbO4-delta/NiO anodes are produced by tape-casting and co-lamination of green layers. Their. porosity is finely tuned by using a pyrolyzable pore former. La0.995Sr0.005NbO4-delta electrolytes are spin-coated using ceramic-based suspensions. Fully dense electrolytes with thickness ranging from 9 mu m to 26 mu m are obtained after sintering in air at 1350 degrees C. The cathode layers are then screen-printed. To match thermal expansion and to avoid chemical reaction between the functional layers, special attention is paid to the design of cathode architectures. CaTi0.9Fe0.1O3-delta, La2NiO4+delta and La4Ni3O10 mixed oxygen ion and electron conducting oxides are investigated as either monophase or La-0.995 Sr-0.005 NbO4-delta-based composite electrodes. The latter gives the whole cell an innovative semi-monolithic concept, which can take advantage of the chemical and mechanical stability of La0.995Sr0.005NbO4-delta, as well as of inherent material integration. Most promising cell architectures are finally selected based on thermo-mechanical and chemical compatibility of all functional layers. (C) 2008 Elsevier B.V. All rights reserved.